Carbon-deposited alkali metal oxyanion electrode material and process for preparing same

ABSTRACT

The present invention relates to a process for the synthesis of a carbon-deposited alkali metal oxyanion cathode material comprising particles, wherein said particles carry, on at least a portion of the particle surface, carbon deposited by pyrolysis, said process comprising a dry high-energy milling step performed on precursors of said carbon-deposited alkali metal oxyanion prior to a solid-state thermal reaction.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.13/294,853, filed on Nov. 11, 2011, which claims the benefit of U.S.Provisional Patent Application No. 61/412,547 filed on Nov. 11, 2010,and which are each incorporated by reference in their entirety hereinfor any and all purposes.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to the field of electrode materials, andmore specifically, to a carbon-deposited alkali metal oxyanion electrodematerial as well as to a process for preparing same.

2. Description of the Related Art

Positive electrodes of lithium-ion battery generally comprise anelectrochemically active cathode material, a binder and carbon particleswhich act as an electronically conductive additive. During batterycycling, it has been observed that such positive electrodes generallyshow a deleterious increase in electrode resistance. It has beenproposed that as the number of cycles increases, the cathode materialexhibits unit lattice volume expansion/shrinkage variations that are dueto insertion/deinsertion of alkali cation in the cathode material. It isbelieved that these variations induce a loss of electronicallyconductive network contact with the cathode material and/or breaking ofcathode material particles. As a result, the battery's capacitydecreases and the battery has a resulting shorter life span.

To address this problem, it has been proposed to fine-tune thecomposition of cathode materials in order to reduce the observed changeof unit cell volume concomitant to alkali cation insertion/deinsertion.

WO 2009/096255 (assigned to Sharp Kabushiki Kaisha), which isincorporated herein by reference in its entirety, describes aLi_(y)K_(a)Fe_(1-x)X_(x)PO₄ cathode material with reduced change of theunit cell volume, where X represents at least one element selected fromgroup 2 to 13 elements; a and x are 0<a≦0.25 and 0≦x≦0.25, respectively;and y is (1−a).

WO 2010/134579 (assigned to Sharp Kabushiki Kaisha), which isincorporated herein by reference in its entirety, describes an alkalimetal phosphosilicate material of general formulaLiFe_(1-x)M_(x)P_(1-y)Si_(y)O₄ where the average valency of Fe is +2 orgreater; M is an element having a valency of +2 or greater and is atleast one selected from the group consisting of Zr, Sn, Y and Al; thevalency of M and the average valency of Fe are different; 0<x≦0.5; andy=x*(valency of M−2)+(1−x)*(average valency of Fe−2).

JP 2011/77030 (assigned to Sharp Corp. and Kyoto University), which isincorporated herein by reference in its entirety, describes an alkalimetal phosphosilicate material of general formulaLi_((1-a))A_(a)Fe_((1-x-b))M_((x-c))P_((1-y))Si_(y)O₄ where A is atleast one kind selected from a group consisting of Na, K, Fe and M.Average valence of Fe is +2 or more, M is an element of valence of +2 ormore, and at least one kind selected from a group consisting of Zr, Sn,Y and Al, the average valence of M and the average valence of Fe aredifferent from each other, 0<a≦0.125, the total number of moles of Naand K in A is d, number of moles of Fe in A is b, number of moles of Min A is c, a=b+c+d, 0<x≦0.5, and 0<y≦0.5.

SUMMARY OF THE INVENTION

In one broad aspect, the present invention relates to carbon-depositedalkali metal oxyanion cathode materials and to a process for obtainingsame.

In another broad aspect, the present invention relates to a process forthe synthesis of a carbon-deposited alkali metal oxyanion electrodematerial, which includes at least one thermal step, where a dryhigh-energy milling step of the carbon-deposited alkali metal oxyanionelectrode material precursors is performed prior to the at least onethermal step.

In yet another broad aspect, the present invention relates to a processfor the synthesis of a carbon-deposited alkali metal oxyanion cathodematerial comprising particles, where the particles carry, on at least aportion of the particle surface, carbon deposited by pyrolysis, theprocess comprising: a first dry high-energy milling step on precursorsof the carbon-deposited alkali metal oxyanion prior to a firstsolid-state thermal reaction to produce a first solid-state thermalreaction product; and a second dry high-energy milling step on theproduct prior to a second solid-state thermal reaction.

These and other aspects and features of the present invention will nowbecome apparent to those of ordinary skill in the art upon review of thefollowing description of specific embodiments of the invention inconjunction with the accompanying figures.

BRIEF DESCRIPTION OF THE FIGURES

A detailed description of examples of implementation of the presentinvention is provided hereafter, by way of example only, with referenceto the accompanying figures, in which:

FIG. 1 represents the XRD spectrum (CoKα) of carbon-deposited lithiumiron zirconium phosphosilicate, obtained from FePO₄, iron oxalate,Li₂CO₃, Si(OC₂H₅)₄, Zr(IV) acetate hydroxide, at an atomic ratioLi:Fe:Zr:P:Si=1:0.9:0.1:0.8:0.2, as prepared in example 1. Unit cellvolume calculated from XRD data is 291 Å³ comparatively to 291 Å³ forC—LiFePO₄.

FIG. 2 represents the XRD spectrum (CoKα) of carbon-deposited lithiumiron zirconium phosphosilicate, obtained from FePO₄, iron oxalate,Li₂CO₃, Si(OC₂H₅)₄, Zr(IV) acetate hydroxide, at an atomic ratioLi:Fe:Zr:P:Si=1:0.9:0.1:0.8:0.2, as prepared in example 2. Unit cellvolume calculated from XRD data is 291.1 Å³ comparatively to 291 Å³ forC—LiFePO₄.

FIG. 3 represents the XRD spectrum (CoKα) of carbon-deposited lithiumiron zirconium phosphosilicate, obtained from FePO₄, iron oxalate,Li₂CO₃, Si(OC₂H₅)₄, Zr(IV) acetate hydroxide, at an atomic ratioLi:Fe:Zr:P:Si=1:0.9:0.1:0.8:0.2, as prepared in example 3. Unit cellvolume calculated from XRD data is 291.8 Å³ comparatively to 291 Å³ forC—LiFePO₄.

FIG. 4 represents the XRD spectrum (CoKα) of carbon-deposited lithiumiron zirconium phosphosilicate, obtained from FePO₄, iron oxalate,Li₂CO₃, Si(OC₂H₅)₄, Zr(IV) acetate hydroxide, at an atomic ratioLi:Fe:Zr:P:Si=1:0.9:0.1:0.8:0.2, as prepared in example 4. Unit cellvolume calculated from XRD data is 292.6 Å³ comparatively to 291 Å³ forC—LiFePO₄.

FIG. 5 represents the XRD spectrum (CoKα) of carbon-deposited lithiumiron zirconium phosphosilicate, obtained from iron oxalate, LiH₂PO₄,Li₂CO₃, Si(OC₂H₅)₄, Zr(IV) acetate hydroxide, at an atomic ratioLi:Fe:Zr:P:Si=1:0.95:0.05:0.95:0.05, as prepared in example 5. Unit cellvolume calculated from XRD data is 291.3 Å³ comparatively to 291 Å³ forC—LiFePO₄.

FIG. 6 represents the XRD spectrum (CoKα) of carbon-deposited lithiumiron zirconium phosphosilicate, obtained from iron oxalate, LiH₂PO₄,Li₂CO₃, Si(OC₂H₅)₄, Zr(IV) acetate hydroxide, at an atomic ratioLi:Fe:Zr:P:Si=1:0.95:0.05:0.9:0.1, as prepared in example 5. Unit cellvolume calculated from XRD data is 291.6 Å³ comparatively to 291 Å³ forC—LiFePO₄.

FIG. 7 represents cathode capacity, determined at room temperature andC/12, C and 10 C discharge rate, for a Li/1M LiPF₆ EC:DEC3:7/carbon-deposited lithium iron zirconium phosphosilicate battery.Battery voltage (in Volt vs Li⁺/Li) is indicated on Y axis and capacity(in mAh/g) is indicated on X axis. Battery has been prepared with apositive electrode containing a cathode material embodiment of thepresent invention prepared in example 2.

FIG. 8 represents cathode capacity, determined at room temperature andC/12, C and 10 C discharge rate, for a Li/1M LiPF₆ EC:DEC3:7/carbon-deposited lithium iron zirconium phosphosilicate battery.Battery voltage (in Volt vs Li⁺/Li) is indicated on Y axis and capacity(in mAh/g) is indicated on X axis. Battery has been prepared with apositive electrode containing a carbon-deposited lithium iron zirconiumphosphosilicate embodiment of the present invention, at an atomic ratioLi:Fe:Zr:P:Si=1:0.95:0.05:0.9:0.1, prepared in example 5.

FIG. 9 represents cathode capacity, determined at room temperature andC/12, C and 10 C discharge rate, for a Li/1M LiPF₆ EC:DEC3:7/carbon-deposited lithium iron zirconium phosphosilicate battery.Battery voltage (in Volt vs Li⁺/Li) is indicated on Y axis and capacity(in mAh/g) is indicated on X axis. Battery has been prepared with apositive electrode containing a carbon-deposited lithium iron zirconiumphosphosilicate embodiment of the present invention, at an atomic ratioLi:Fe:Zr:P:Si=1:0.95:0.05:0.95:0.05, prepared in example 5.

FIG. 10 represents battery power capability (ragone plot), determined atroom temperature, for a Li/1M LiPF₆ EC:DEC 3:7/carbon-deposited lithiumiron zirconium phosphosilicate battery. Capacity (in mAh/g) is indicatedon Y axis and discharge rate (C-rate; a 1 C rate corresponding todischarge of full capacity in 1 hour) is indicated on X axis, initialcapacity is determined by slow-scan voltammetry. Battery has beenprepared with a positive electrode containing a carbon-deposited lithiumiron zirconium phosphosilicate embodiment of the present invention, atan atomic ratio Li:Fe:Zr:P:Si=1:0.95:0.05:0.95:0.05, prepared in example5.

FIG. 11 illustrates cycling capability, determined at 60° C. and C/4discharge rate, for a Li/1M LiPF₆ EC:DEC 3:7/C—LiFePO₄ carbon-depositedlithium iron zirconium phosphosilicate battery. Battery capacity (inmAh/g) is indicated on Y axis and cycle number is indicated on X axis,initial capacity is determined by slow-scan voltammetry. Battery hasbeen prepared with a positive electrode containing a carbon-depositedlithium iron zirconium phosphosilicate embodiment of the presentinvention, at an atomic ratio Li:Fe:Zr:P:Si=1:0.95:0.05:0.95:0.05,prepared in example 5. The square represent the battery capacity and thecircles represent the ratio charge/discharge.

DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

The present inventors have surprisingly and unexpectedly discovered,during an R&D project initiated to synthesize a specificcarbon-deposited alkali metal phosphosilicate,C—LiFe_(0.9)Zr_(0.01)(PO₄)_(0.9)(SiO₄)_(0.1), that known processes forobtaining carbon-deposited alkali metal oxyanion, such as those reportedfor the specific case of C—LiFePO₄, e.g. wet-process, solid-statethermal process, polyol process, etc. produce low-quality materials.

The present invention relates to carbon-deposited alkali metal oxyanioncathode materials and to a process for obtaining same. In onenon-limiting embodiment, the carbon-deposited alkali metal oxyanioncathode material of the present invention enables one to obtain acathode having such properties that prevents and/or minimizes theexpansion/shrinkage of the cathode. It is thus possible toprevent/minimize the internal resistance of the battery from increasingas the number of charging/discharging cycles increases. It is thereforepossible to produce a cathode active material which allows production ofa battery which not only excels in terms of safety and cost, but alsohas a longer life.

In one non-limiting embodiment, the present invention relates to aprocess for the synthesis of a carbon-deposited alkali metal oxyanionelectrode material, which includes at least one thermal step and a dryhigh-energy milling step of reactants performed prior to the at leastone thermal step.

In another non-limiting embodiment, the present invention relates to aprocess for the synthesis of a carbon-deposited alkali metal oxyanionelectrode material, which includes a first dry high-energy milling stepof the carbon-deposited alkali metal oxyanion electrode materialprecursors that is performed prior to a first thermal step, and includesa second dry high-energy milling step of the product obtained after thefirst thermal step, where the second high-energy milling step isperformed prior to a second thermal step.

In another non-limiting embodiment, the process includes a step ofpyrolysis of a source of carbon for obtaining a carbon deposit onto thealkali oxyanion material and/or its precursors. In one non-limitingembodiment, the pyrolysis can be performed during the herein describedfirst thermal step and/or second thermal step. In another non-limitingembodiment, an optional flash pyrolysis is performed after the synthesisreaction to improve carbon deposit graphitization.

The deposit of carbon can present a more or less uniform, adherent andnon-powdery deposit. In one non-limiting embodiment, the carbon depositrepresents up to 15% by weight, with respect to the total weight of thematerial. In another embodiment, the carbon deposit represents from 0.5to 5% by weight with respect to the total weight of the material.Deposition of carbon by pyrolysis of a carbon source can be performed onthe end product and/or on its precursors as described, for instance, inWO 02/027824, WO 02/027823, CA 2,307,119, WO 2011/072397, US 2002/195591and US 2004/157126, which are incorporated herein by reference in theirentirety.

In a non-limiting implementation, performed at an industrial scale, theprocess of the invention can be carried out continuously or in batch, ina reactor selected from rotary kilns, push kilns, fluidized beds,belt-driven kilns, that allow control of the composition and thecirculation of the gaseous atmosphere. Utilization of large batch kiln,such as baking kiln, is not excluded. The person skilled in the art willbe able to identify any alternative suitable alternative reactors or anyfrom the above without departing from the present invention.

In mechanochemistry, the term “high-energy milling” is usually used inorder to stress the character of applied milling equipments (mills) usedfor preparation of micro- and nanosized solids. (See, e.g., P. Balaz,Mechanochemistry in Nanoscience and Minerals Engineering, Chapter 2,Springer-Verlag Berlin Heidelberg 2008; De Castro and Mitchell,Synthesis, Functionalization and surface treatment of nanoparticles,Chapter 1, American Scientific Publishers 2002; Zoz, Ren, Reichardt andBenz, High Energy Milling/Mechanical Alloying/Reactive Milling, ZozGmbH, available on Zoz website at“http://www.zoz-group.de/zoz.engl/zoz.main/pdfcontent/publications/v14.pdf”—which are each incorporated herein byreference in their entirety).

High-energy milling of the precursors, can be performed with a largechoice of equipments, for example without any limitation, high-energyball mills, pulverizing mixer mills, planetary ball mills,drum/ball-mills, shaker mills, stirred ball mills, mixer ball mills,vertical and horizontal attritors, and equivalent milling equipments.The person skill in the art is able to identify suitable equipmentswithout undue experimentation and without departing from the presentinvention. High-energy milling equipments are commercially available,for example but without any limitation, from SPEX CertiPrep Group L.L.C.(8000M Mixer/Mill®, etc.), Zoz GmbH (Simoloyer®), Retsch GmbH (PlanetaryBall Mill PM 200/400/400 MA) and Union Process Inc. (Attritor®).

In one non-limiting embodiment, the high-energy milling equipment isselected to avoid contamination of reactants, especially metalliccontamination. To perform metal-free grinding, milling parts of theequipment are preferably made of ceramics, or coated with ceramics, forexample, without any limitation, alumina, zirconium silicate, zirconia,yttria or ceria stabilized zirconia, silicium nitride, tungsten carbideor silicium carbide. The person skill in the art is able to identify anyalternative suitable milling parts of the equipment or any from theabove without departing from the present invention.

In one non-limiting embodiment, the high-energy milling is high-energyball milling.

In one non-limiting embodiment, the process of the invention includes afirst solid-state thermal step operated at a temperature selected fromthe following temperature ranges of between about 200° C. and about 600°C., about 250° C. and about 600° C., about 275° C. and about 600° C.,about 300° C. and about 600° C., about 325° C. and about 600° C., about350° C. and about 600° C., or about 375° C. and about 600° C., or about400° C. and about 600° C., or about 200° C. and about 500° C., or about250° C. and about 450° C., or about 300° C. and about 400° C. The personskilled in the art will be able to select any alternative suitabletemperature or any temperature falling within any of the ranges abovewithout departing from the spirit of the invention.

In one non-limiting embodiment, the process of the invention includes asecond solid-state thermal step operated at a temperature selected fromthe following temperature ranges of between about 400° C. and about 800°C., about 450° C. and about 800° C., about 500° C. and about 800° C.,about 525° C. and about 800° C., about 550° C. and about 800° C., orabout 575° C. and about 800° C., or about 600° C. and about 800° C., orabout 400° C. and about 700° C., or about 450° C. and about 650° C., orabout 500° C. and about 600° C. The person skilled in the art will beable to select any alternative suitable temperature or any temperaturefalling within any of the ranges above without departing from the spiritof the invention.

In one non-limiting embodiment, the process of the invention includes afirst high-energy milling step that is performed during a time periodselected from the following time ranges of between about 5 minutes toabout 4 hours, about 10 minutes to about 4 hours, about 30 minutes toabout 4 hours, about 60 minutes to about 4 hours, about 90 minutes toabout 4 hours, about 120 minutes to about 4 hours, about 150 minutes toabout 4 hours, about 180 minutes to about 4 hours, about 210 minutes toabout 4 hours, or about 230 minutes to about 4 hours. The person skilledin the art will be able to select any alternative suitable time periodor any time period falling within any of the ranges above withoutdeparting from the spirit of the invention.

In one non-limiting embodiment, the process of the invention includes asecond high-energy milling that is performed during a time periodselected from the following time ranges of between about 5 minutes toabout 4 hours, about 10 minutes to about 4 hours, about 30 minutes toabout 4 hours, about 45 minutes to about 4 hours, about 60 minutes toabout 4 hours, about 90 minutes to about 4 hours, about 120 minutes toabout 4 hours, about 150 minutes to about 4 hours, about 180 minutes toabout 4 hours, about 210 minutes to about 4 hours, or about 230 minutesto about 4 hours. The person skilled in the art will be able to selectany alternative suitable time period or any time period falling withinany of the ranges above without departing from the spirit of theinvention.

In one non-limiting embodiment, the process of the invention includes asubsequent flash thermal treatment on the oxyanion end-product in orderto improve the graphitization of carbon deposit while avoiding partialdecomposition of the oxyanion. The flash thermal treatment can beoperated at a temperature selected from the following temperature rangesof between about 650° C. and about 900° C., about 700° C. and about 900°C., about 750° C. and about 900° C., about 800° C. and about 900° C., orabout 825° C. and about 900° C., or about 850° C. and about 900° C. Theperson skilled in the art will be able to select any alternativesuitable temperature or any temperature falling within any of the rangesabove without departing from the spirit of the invention.

The flash thermal treatment can be operated during a period of timeselected from the following time ranges of between about 10 seconds andabout ten minutes, about 30 seconds and about ten minutes, about oneminute and about ten minutes, about two minutes and about ten minutes,about three minutes and about ten minutes, about four minutes and aboutten minutes, or about five minutes and about ten minutes. The personskilled in the art will be able to select any alternative suitable timeperiod or any time period falling within any of the ranges above withoutdeparting from the spirit of the invention.

In one non-limiting embodiment, the herein described high-energy millingstep produces a substantially amorphous product. The substantiallyamorphous product then becomes a substantially crystalline product afterthe herein described thermal reaction performed at a sufficiently hightemperature. The person skilled in the art will be able to select asuitable temperature without departing from the invention.

In one non-limiting embodiment, the herein described first thermalreaction and/or second high-energy milling step produces a substantiallyamorphous product, which then becomes a substantially crystallineproduct after the herein described second thermal reaction which isperformed at a sufficiently high temperature. The person skilled in theart will be able to select a suitable temperature without departing fromthe invention.

In one non-limiting embodiment, the herein described oxyanion is aphosphosilicate.

In one non-limiting embodiment, the process of the invention includesreacting precursors of a carbon-deposited alkali metal phosphosilicatecathode material, where the precursors comprise:

-   a) at least one source compound of an alkali metal;-   b) at least one source compound of a metal M selected from Fe and/or    Mn;-   c) at least one source compound of a metal M′, where M′ in the final    product is a 2+ or more metal;-   d) at least one source compound of P, if the element P is not    present in another source compound; and-   e) at least one source compound of Si, if the element Si is not    present in another source compound.-   f) at least one source compound of carbon.

In one non-limiting embodiment, the source compound of carbon is presentprior to the herein described first thermal step and/or prior to theherein described second thermal step.

In one non-limiting embodiment, the herein described source compoundsare totally present for the herein described first thermal step, or anypart thereof is present for each of the herein described first andsecond thermal step. In other words, the person skilled in the art willunderstand that the process may include addition of one or more of theherein described source compound during/prior to the second high-energymilling and/or second thermal step.

In one non-limiting embodiment the source compound b) is partiallyreplaced by at most 15% of: one or more other metals selected from Niand Co, and/or atoms of one or more aliovalent or isovalent metals otherthan Ni or Co, and/or atoms of Fe(III).

In another non-limiting embodiment the source compound b) is partiallyreplaced by at most 15% of: one or more other metals chosen from Ni andCo, and/or by one or more aliovalent or isovalent metals selected fromthe group consisting of Mg, Mo, Mn, V, Pb, Sn, Nb, Ti, Al, Ta, Ge, La,Y, Yb, Cu, Ag, Sm, Ce, Hf, Cr, Zr, Bi, Zn, Ca, B and W, and/or atoms ofFe(III).

In the present invention, the “one or more metal” described herein isreadily understood by the person skilled in the art as being one or moremetal of those metals which are suitable in the art of batteries. Forexample, but without being limited thereto, the “one or more metal”described herein may be selected from any metal included in the 2, 3, 4,5, or 6 periods from the periodic table that are suitable in the art ofbatteries without departing from the invention. In another example, butwithout being limited thereto, the “one or more metal” described hereinmay be selected from at least one element selected from group 2 to 13elements. In another example, but without being limited thereto, the“one or more metal” described herein may be selected from Mg, Mo, Mn, V,Co, Ni, Pb, Sn, Nb, Ti, Al, Ta, Ge, La, Y, Yb, Cu, Ag, Sm, Ce, Hf, Cr,Zr, Bi, Zn, Ca, B and W. The person skilled in the art will be able toselect any alternative suitable “one or more other metal” or any fromthe above without departing from the present invention.

In one non-limiting embodiment, the carbon-deposited alkali metalphosphosilicate of the invention is characterized in that a cathodematerial containing this material exhibits reduced change of the unitcell (lattice) volume concomitant to alkali cationinsertion/deinsertion. In one aspect, the reduction of the unit cell(lattice) volume change can be characterized by the volume change of thede-cationated (e.g. delithiated) product versus the cationated (e.g.lithiated) product. In one non-limiting embodiment, the unit (lattice)volume of a given product can be evaluated by an XRD measurement of theproduct. In one non-limiting implementation of this concept, the presentinventors measured the increase in unit (lattice) cell volume of a givenproduct relatively to the unit (lattice) cell volume of C—LiFePO₄ as aparameter to evaluate the performance of a given synthesis process. Forexample, an end-product with an unsuitable increase in unit cell volumewas characterized as representing a cathode material of low purityand/or inadequate substitution and/or presence of the M′ in thephosphosilicate matrix.

In one non-limiting embodiment, the source compound a) is an alkalicompound selected, for example, from the group consisting of lithiumoxide, sodium oxide, lithium hydroxide, sodium hydroxide, potassiumhydroxide, lithium carbonate, sodium carbonate, potassium carbonate,Li₃PO₄, Na₃PO₄, K₃PO₄, the hydrogen phosphate LiH₂PO₄, LiNaHPO₄,LiKHPO₄, NaH₂PO₄, KH₂PO₄, Li₂HPO₄, lithium, sodium or potassium ortho-,meta- or polysilicates, lithium sulfate, sodium sulfate, potassiumsulfate, lithium oxalate, sodium oxalate, potassium oxalate, lithiumacetate, sodium acetate, potassium acetate and one of their mixtures.The person skilled in the art will be able to select any alternativesuitable source compound a) or any from the above without departing fromthe spirit of the invention.

In one non-limiting embodiment, the source compound b) comprise acompound selected, for example, from iron, iron(III) oxide or magnetite,trivalent iron phosphate, lithium iron hydroxyphosphate or trivalentiron nitrate, ferrous phosphate, hydrated or nonhydrated, vivianiteFe₃(PO₄)₂, iron acetate (CH₃COO)₂Fe, iron sulfate (FeSO₄), iron oxalate,iron(III) nitrate, iron(II) nitrate, FeCl₃, FeCl₂, FeO, ammonium ironphosphate (NH₄FePO₄), Fe₂P₂O₇, ferrocene or one of their mixtures;and/or manganese, MnO, MnO₂, manganese acetate, manganese oxalate,Mn(III) acetylacetonate, Mn(II) acetylacetonate, Mn(II) chloride, MnCO₃,manganese sulfate, manganese nitrate, manganese phosphate, manganoceneor one of their mixtures. The person skilled in the art will be able toselect any alternative suitable source compound b) or any from the abovewithout departing from the spirit of the invention.

In one non-limiting embodiment, the source compound c) is a sourcecompound of a metal which in the final product is a metal having avalency of 2+ or more. For example, it is a source compound of a metalselected from the group consisting of Zr⁴⁺, Ti⁴⁺, Nb⁴⁺, Mo⁴⁺, Ge⁴⁺, Ce⁴⁺and Sn⁴⁺, and/or a source compound a metal selected from the groupconsisting of Al³⁺, Y³⁺, Nb³⁺, Ti³⁺, Ga³⁺, Cr³⁺ and V³⁺, and/or a sourcecompound a metal selected from the group consisting of Ta⁵⁺ and Nb⁵⁺,and/or a source compound a metal selected from the group consisting ofZn²⁺ and Ca²⁺. For example, in the specific case of a source compound ofa valency 2+, the source compound c) may be selected from zinc acetate,zinc chloride, zinc acetylacetonate, zinc nitrate, zinc sulfate, zincstearate, calcium carbonate, calcium hydroxide, calcium acetate, or amixture thereof. For example, in the specific case of a source compoundof valency 3+, the source compound c) may be selected from yttrium(III)2-ethylhexanoate, yttrium(III) acetate, yttrium(III) acetylacetonate,yttrium(III) nitrate, aluminum acetate, aluminum isopropoxide, aluminumacetylacetonate, aluminum ethoxide, aluminum metaphosphate, aluminummonostearate, or a mixture thereof. For example, in the specific case ofa source compound of valency 4+, the source compound c) may be selectedfrom zirconium acetate hydroxide, zirconium alkoxide, zirconium(IV)acetylacetonate, zirconium(IV) ethoxide, zirconium(IV)hydrogenphosphate, zirconium(IV) silicate, titanium(IV)2-ethylhexyloxide, titanium(IV) butoxide, germanium(IV) ethoxide,tin(IV) acetate, or a mixture thereof. For example, in the specific caseof a source compound of valency 5+, the source compound c) may beselected from tantalum(V) butoxide, niobium(V) ethoxide, niobium(V)phenoxide, or a mixture thereof. The person skilled in the art will beable to select any alternative suitable source compound c) or any fromthe above without departing from the spirit of the invention.

In one non-limiting embodiment, the source compound d) is a compound ofphosphorus selected, for example, from phosphoric acid and its esters,M₃PO₄ wherein M is at least one selected from Li, Na and K, the hydrogenphosphate MH₂PO₄ wherein M is at least one selected from Li, Na and K,monoammonium or diammonium phosphates, trivalent iron phosphate ormanganese ammonium phosphate (NH₄MnPO₄), MnHPO₄, Fe₂P₂O₇. The personskilled in the art will be able to select any alternative suitablesource compound d) or any from the above without departing from thespirit of the invention.

In one non-limiting embodiment, the source compound e) is a compound ofsilicon selected, for example, from organosilicon, silicon alkoxides,tetraethyl orthosilicate, nanosized SiO₂, Li₂SiO₃, Li₄SiO₄ or a mixturethereof. The person skilled in the art will be able to select anyalternative suitable source compound e) or any from the above withoutdeparting from the spirit of the invention.

In one non-limiting embodiment, a subset or all of the source compoundsa) to e) can also be additionally a source of oxygen and/or a source ofat least two elements.

The person skilled in the art will be able to determine the ratiosrequired for each of the source compound depending on the desiredcarbon-deposited alkali metal oxyanion product without departing fromthe spirit of the invention. For example, in the case of acarbon-deposited alkali metal phosphosilicate product, the sourcecompounds are selected to provide a cathode material having alkalimetal:M:M′:P:Si ratios of about 1:0.7 to 1:>0 to 0.3:>0.7 to 1:>0 to0.3, where “>0” does not include 0, rather it means “more than 0”.

The deposition of carbon on the surface of the alkali metal oxyanion orits precursors is obtained by pyrolysis of the source compound of carbonf). The deposition of carbon at the surface of the oxyanion or itsprecursors can be obtained by thermal decomposition or transformation ofhighly varied source compounds of carbon. In one non-limitingembodiment, the source compound of carbon is a compound which is in theliquid state or in the gas state, a compound which can be used in theform of a solution in liquid solvent, or a compound which changes to theliquid or gas state during its thermal decomposition or transformation,so as to more or less coat the compounds in the mixture. The sourcecompound of carbon can, for example, be chosen from liquid, solid orgaseous hydrocarbons and their derivatives (in particular polycyclicaromatic entities, such as tar or pitch), perylene and its derivatives,polyhydric compounds (for example, sugars and carbohydrates, and theirderivatives), polymers, cellulose, starch and their esters and ethers,fatty acid salts (for example stearic, oleic acid or lithium stearate),fatty acid esters, fatty alcohol esters, alkoxylated alcohols,alkoxylated amines, fatty alcohol sulfate or phosphate esters,imidazolium and quaternary ammonium salts, ethylene oxide/propyleneoxide copolymer, ethylene oxide/butylene oxide copolymer and theirmixtures. Mention may be made, as examples of polymers, of polyolefins,polyethylene, polypropylene, polybutadienes, polyvinyl alcohol,condensation products of phenols (including those obtained from reactionwith aldehydes), polymers derived from furfuryl alcohol, from styrene,from divinylbenzene, from naphthalene, from perylene, from acrylonitrileand from vinyl acetate. A non-limiting example is Unithox™ 550ethoxylate (Baker Hughes). Unithox™ ethoxylates are nonionic emulsifiersand wetting agents with high molecular weights and melt points. TheseBaker Petrolite ethoxylated products are produced from Unilin™ alcoholswhich are fully saturated, long chain, linear, C₂₀ to C₅₀, syntheticalcohols. The person skilled in the art will be able to select anyalternative suitable source compound of carbon or any from the abovewithout departing from the spirit of the invention.

In one non-limiting embodiment, any of the herein described processsteps are performed under an inert atmosphere such as, without anylimitation, nitrogen, argon, and/or helium. In one non-limitingembodiment, any of the herein described thermal steps is performed undera humidified atmosphere, for example as described in WO 2011/072397,which is incorporated herein in its entirety.

In one non-limiting embodiment, any of the herein described processsteps are performed under a reductive atmosphere which participates inthe reduction and/or prevents the oxidation of the oxidation state of atleast one metal in the precursors without full reduction to an elementalstate. For example, the reductive atmosphere is present during the firsthigh-energy milling step, the second high-energy milling step, the firstthermal step, the second thermal step, or any combinations thereof.

In one non-limiting embodiment, the reductive atmosphere is, but withoutbeing limited thereto, an externally applied reductive atmosphere, areductive atmosphere derived from the degradation of a source compound,or a reductive atmosphere derived from the synthesis reaction.

In one non-limiting embodiment, the above externally applied reductiveatmosphere comprises a gas such as, but without being limited thereto,CO, H₂, NH₃, HC, and any combinations thereof, which participates in thereduction or prevents the oxidation of the oxidation state of at leastone metal in the precursors without full reduction to an elemental stateand where HC refers to any hydrocarbon or carbonaceous product in gas orvapor form. The externally applied reductive atmosphere can alsocomprise an inert gas such as, but without being limited thereto, CO₂,N₂, argon, helium, nitrogen or other inert gases.

In one non-limiting embodiment, the above reductive atmosphere derivedfrom the degradation of a source compound is, but without being limitedthereto, a reductive atmosphere which is produced when the sourcecompound is degraded or is transformed during a thermal step.

In one non-limiting embodiment, this compound is a reducing agent sourcewhich is degraded or is transformed during the thermal step and producesa reductive atmosphere which participates in the reduction or preventsthe oxidation of the oxidation state of at least one metal in theprecursors without full reduction to an elemental state. In onenon-limiting embodiment, this reductive atmosphere comprises CO, CO/CO₂,H₂, or any combinations thereof.

In one non-limiting embodiment, the above reductive atmosphere derivedfrom the synthesis reaction is, but without being limited thereto, areductive atmosphere that is produced during a thermal step, and whichparticipates in the reduction or prevents the oxidation of the oxidationstate of at least one metal in the precursors without full reduction toan elemental state. In one non-limiting embodiment, this reductiveatmosphere comprises CO, CO/CO₂, H₂ or any combinations thereof.

In accordance with a specific non-limiting implementation, thecarbon-deposited alkaline metal oxyanion material of the presentinvention may comprise at its surface and/or in the bulk, additives,such as, without any limitation, carbon particles, carbon fibers andnanofibers, carbon nanotubes, graphene, vapor growth conductive fiber(VGCF), metallic oxides, and any mixtures thereof. Those additives couldbe in any form including spherical (granular) form, flaky form, afibrous form and the like. Those additives may be incorporated into theprocess at any step, for example in a two-step thermal process theseadditives could be incorporated prior to the first and/or the secondthermal step.

By “general formula” one means that the stoichiometry of the materialcan vary by a few percents from stoichiometry due, for example butwithout being limited thereto, to substitution or other defects presentin the material structure, including anti-sites structural defects suchas, without any limitation, cation disorder between iron and lithium incathode material crystal, see for example Maier et al. [Defect Chemistryof LiFePO₄, Journal of the Electrochemical Society, 155, 4, A339-A344,2008] and Nazar et al. [Proof of Supervalent Doping in Olivine LiFePO₄,Chemistry of Materials, 2008, 20 (20), 6313-6315].

The present inventors have discovered that the carbon-deposited alkalimetal phosphosilicate cathode material of the present invention can beoptimized by optimizing the precursors' ratios. While the inventorsnoticed that a possible resulting theoretical chemical formula mayslightly depart from electroneutrality, without being bond by anytheory, it is believed that the carbon-deposited alkali metalphosphosilicate cathode material of the present invention may containdifferent phases that balance out the material overall charge in orderto ultimately obtain overall electroneutrality. Hence, the presentinvention is not limited to any defined theoretical chemical formulasince the person skilled in the art will understand how to optimize theprecursors' ratios in order to obtain the desired carbon-depositedalkali metal phosphosilicate cathode material of the present inventionwithout departing from the invention.

In one non-limiting embodiment, the present invention relates to acarbon-deposited alkali metal phosphosilicate cathode material,comprising particles which carry, on at least a portion of theirsurface, carbon deposited by pyrolysis.

In one non-limiting embodiment, the particles have an olivine structure.However, the scope of the present invention is not limited to anarrangement having an olivine structure. Thus, an arrangement not havingan olivine structure is also within the scope of the present invention.

In one non-limiting embodiment, the carbon-deposited alkali metalphosphosilicate cathode material, comprises a metal that has a valenceof 2+. For example, the carbon-deposited alkali metal phosphosilicatecathode material comprises Fe(II) and/or Mn(II).

In one non-limiting embodiment, the present invention relates to acarbon-deposited alkali metal phosphosilicate cathode material,comprising particles which carry, on at least a portion of theirsurface, carbon deposited by pyrolysis, where the particles have ageneral formula A_(z)M_(1-x)M′_(x)P_(1-y)Si_(y)O₄ where the averagevalency of M is +2 or greater; M is Fe and/or Mn; and A is at least onealkali metal selected from Li, Na and K. Optionally, the Fe and/or Mn issubstituted by at most 15% at. of one or more metal at oxidation levelsbetween +1 and +5. M′ is a metal of valency of 2+ or more. The x, y andz are defined as follows: 0.8≦z≦1.2; 0<x≦0.25; and y=x*(valency ofM′−2)+(1−x)*(average valency of M−2).

In one non-limiting embodiment, z is: 0.9≦z≦1.1.

In another non-limiting embodiment, z is: 0.95≦z≦1.05.

In yet another non-limiting embodiment, z is: 0.97≦z≦1.03.

In yet another non-limiting embodiment, z is: 0.98≦z≦1.02.

In a non-limiting embodiment, the present invention relates to acarbon-deposited alkali metal phosphosilicate cathode material,comprising particles which carry, on at least a portion of theirsurface, carbon deposited by pyrolysis, where the particles have ageneral formula AM_(1-x)M′_(x)P_(1-y)Si_(y)O₄ where the average valencyof M is +2 or greater; M is Fe and/or Mn; and A is at least one alkalimetal selected from Li, Na and K. Optionally, the Fe and/or Mn issubstituted by at most 15% at. of one or more metal at oxidation levelsbetween +1 and +5. M′ is a metal of valency of 2+ or more. The x, y andz are defined as follows: 0<x≦0.25; and y=x*(valency ofM′−2)+(1−x)*(average valency of M−2).

In a further non-limiting embodiment, the present invention relates to acarbon-deposited alkali metal phosphosilicate cathode material,comprising particles having an olivine structure and which carry, on atleast a portion of their surface, carbon deposited by pyrolysis, wherethe particles have a general formula LiM_(1-x)M′_(x)P_(1-y)Si_(y)O₄where the average valency of M is +2 or greater; M is Fe and/or Mn.Optionally, the Fe and/or Mn is substituted by at most 15% at. of one ormore metal at oxidation levels between +1 and +5. M′ is a metal ofvalency of 2+ or more. The x, y and z are defined as follows: 0<x≦0.25;and y=x*(valency of M′−2)+(1−x)*(average valency of M−2).

In the present invention, the phosphate polyanion (PO₄) and/or SiO₄ canalso be partly substituted by another XO₄ oxyanion, in which X is eitherP, S, V, Si, Nb, Mo or any combinations thereof.

In one non-limiting embodiment, the present invention relates to acarbon-deposited alkali metal phosphosilicate cathode material,comprising particles which carry, on at least a portion of theirsurface, carbon deposited by pyrolysis, where the particles have ageneral element ratios Li:(Fe+Zr):PO₄:SiO₄ of about 1:1:0.7-1:>0-0.3ratios.

In another non-limiting embodiment, the present invention relates to anoptimized carbon-deposited alkali metal phosphosilicate cathodematerial, comprising particles which carry, on at least a portion oftheir surface, carbon deposited by pyrolysis, where the particles have ageneral element ratios Li:Fe:Zr:PO₄:SiO₄, at about1+/−x:0.95+/−x:0.05+/−x:0.95+/−x:0.05+/−x ratios, where x isindependently about 20% of value.

In another non-limiting embodiment, the present invention relates to anoptimized carbon-deposited alkali metal phosphosilicate cathodematerial, comprising particles which carry, on at least a portion oftheir surface, carbon deposited by pyrolysis, where the particles have ageneral element ratios Li:Fe:Zr:PO₄:SiO₄, at about1+/−x:0.95+/−x:0.05+/−x:0.95+/−x:0.05+/−x ratios, where x isindependently about 10% of value.

In one non-limiting embodiment, x is about 5% of value.

In another non-limiting embodiment, x is about 4% of value.

In yet another non-limiting embodiment, x is about 3% of value.

In yet another non-limiting embodiment, x is about 2% of value.

In yet another non-limiting embodiment, the present invention relates toa carbon-deposited alkali metal phosphosilicate cathode material,comprising particles which carry, on at least a portion of theirsurface, carbon deposited by pyrolysis, where the particles have thegeneral formula LiM_(1-x)M′_(x)(PO₄)_(1-2x)(SiO₄)_(2x) where M is Feand/or Mn, and M′ is 4+ metal. Optionally, the phosphate polyanion (PO₄)can also be partly substituted by sulfate polyanion (SO₄) and/or thelithium metal can be partly substituted by Na and/or K.

In yet another non-limiting embodiment, the present invention relates toa carbon-deposited alkali metal phosphosilicate cathode material,comprising particles which carry, on at least a portion of theirsurface, carbon deposited by pyrolysis, where the particles have thegeneral formula LiFe_(1-x)M′_(x)(PO₄)_(1-2x)(SiO₄)_(2x), where M′ is a4+ metal. Optionally, the phosphate polyanion (PO₄) can also be partlysubstituted by sulfate polyanion (SO₄) and/or the lithium metal can bepartly substituted by Na and/or K.

In yet another non-limiting embodiment, the present invention relates toa carbon-deposited alkali metal phosphosilicate cathode material,comprising particles which carry, on at least a portion of theirsurface, carbon deposited by pyrolysis, where the particles have thegeneral formula AM_(1-x)M′_(x)(XO₄)_(1-2x)(SiO₄)_(2x), where:

A is Li, alone or partially replaced by at most 30% as atoms of Naand/or K;

M is a metal comprising at least 90% at. of Fe(II) or Mn(II) or amixture thereof, and at most 10% at. of one or more metal at oxidationlevels between +1 and +5;

M′ is a 4+ valency metal comprising at least one of Zr⁴⁺, Ti⁺, Nb⁴⁺,Mo⁴⁺, Ge⁴⁺, Ce⁴⁺ or Sn⁴⁺;

-   -   XO₄ is PO₄, alone or partially replaced by at most 30 mol % of        SO₄; and 0.03≦x≦0.15.

In yet another non-limiting embodiment, the present invention relates toa carbon-deposited alkali metal phosphosilicate cathode material,comprising particles which carry, on at least a portion of theirsurface, carbon deposited by pyrolysis, where the particles have thegeneral formula AM_(1-x)M′_(x)(XO₄)_(1-2x)(SiO₄)_(2x), where:

A is Li, alone or partially replaced by at most 10% as atoms of Na or K;

M is a metal comprising at least 90% at. of Fe(II) or Mn(II) or amixture thereof, and at most:

-   -   I. 10% as atoms of Ni and/or Co;    -   II. 10% as atoms of one or more aliovalent or isovalent metals        other than Ni or Co;    -   III. 10% as atoms of Fe(III); or    -   IV. any combinations of I. to III.;

M′ is a 4+ valency metal comprising at least one of Zr⁴⁺, Ti⁺, Nb⁴⁺,Mo⁴⁺, Ge⁴⁺, Ce⁴⁺ or Sn⁴⁺;

XO₄ is PO₄, alone or partially replaced by at most 10 mol % of SO₄; and

0.03≦x≦0.15.

In yet another non-limiting embodiment, the present invention relates toa carbon-deposited alkali metal phosphosilicate cathode material,comprising particles which carry, on at least a portion of theirsurface, carbon deposited by pyrolysis, where the particles have thegeneral formula AM_(1-x)M′_(x)(XO₄)_(1-2x)(Si₄)_(2x), where:

A is Li;

M is Fe(II);

M′ is a 4+ valency metal comprising at least one of Zr⁴⁺, Ti⁺, Nb⁴⁺,Mo⁴⁺, Ge⁴⁺, Ce⁴⁺ or Sn⁴⁺;

XO₄ is PO₄; and

0.03≦x≦0.15.

In yet another non-limiting embodiment, the present invention relates toa carbon-deposited alkali metal phosphosilicate cathode material,comprising particles which carry, on at least a portion of theirsurface, carbon deposited by pyrolysis, where the particles have thegeneral formula AM_(1-x)M′_(x)(XO₄)_(1-2x)(SiO₄)_(2x), where:

A is Li;

M is Fe(II);

M′ is Zr⁴⁺;

XO₄ is PO₄; and

0.03≦x≦0.15.

In yet another non-limiting embodiment, the present invention relates toa carbon-deposited alkali metal phosphosilicate cathode material,comprising particles which carry, on at least a portion of theirsurface, carbon deposited by pyrolysis, where the particles have thegeneral formula LiFe_(1-x)Zr_(x)(PO₄)_(1-2x)(SiO₄)_(2x) where0.03≦x≦0.1, or 0.03≦x≦0.08, or 0.04≦x≦0.06.

In yet another non-limiting embodiment, the present invention relates toa carbon-deposited alkali metal phosphosilicate cathode material,comprising particles which carry, on at least a portion of theirsurface, carbon deposited by pyrolysis, where the particles have thegeneral formula LiFe_(0.9)Zr_(0.1)(PO₄)_(0.8)(SiO₄)_(0.2).

In yet another non-limiting embodiment, the present invention relates toa carbon-deposited alkali metal phosphosilicate cathode material,comprising particles which carry, on at least a portion of theirsurface, carbon deposited by pyrolysis, where the particles have thegeneral formula LiM_(1-x)M′_(x)(PO₄)_(1-x)(SiO₄)_(x) where M is Feand/or Mn, and M′ is 3+ metal. Optionally, the phosphate polyanion (PO₄)can also be partly substituted by sulfate polyanion (SO₄) and/or thelithium metal can be partly substituted by Na and/or K.

In yet another non-limiting embodiment, the present invention relates toa carbon-deposited alkali metal phosphosilicate cathode material,comprising particles which carry, on at least a portion of theirsurface, carbon deposited by pyrolysis, where the particles have thegeneral formula LiFe_(1-x)M′_(x)(PO₄)_(1-x)(SiO₄)_(x), where M′ is a 3+metal. Optionally, the phosphate polyanion (PO₄) can also be partlysubstituted by sulfate polyanion (SO₄) and/or the lithium metal can bepartly substituted by Na and/or K.

In yet another non-limiting embodiment, the present invention relates toa carbon-deposited alkali metal phosphosilicate cathode material,comprising particles which carry, on at least a portion of theirsurface, carbon deposited by pyrolysis, where the particles have thegeneral formula AM_(1-x)M′_(x)(XO₄)_(1-x)(SiO₄)_(x), where:

-   -   A is Li, alone or partially replaced by at most 30% as atoms of        Na and/or K;    -   M is a metal comprising at least 90% at. of Fe(II) or Mn(II) or        a mixture thereof, and at most 10% at. of one or more metal at        oxidation levels between +1 and +5;    -   M′ is a 3+ valency metal comprising at least one of Al³⁺, Y³⁺,        Nb³⁺, Ti³⁺, Ga³⁺, Cr³⁺ or V³⁺;    -   XO₄ is PO₄, alone or partially replaced by at most 30 mol % of        SO₄; and    -   0.03≦x≦0.15.

In yet another non-limiting embodiment, the present invention relates toa carbon-deposited alkali metal phosphosilicate cathode material,comprising particles which carry, on at least a portion of theirsurface, carbon deposited by pyrolysis, where the particles have thegeneral formula AM_(1-x)M′_(x)(XO₄)_(1-x)(SiO₄)_(x), where:

-   -   A is Li, alone or partially replaced by at most 10% as atoms of        Na or K;    -   M is a metal comprising at least 90% at. of Fe(II) or Mn(II) or        a mixture thereof, and at most:

I. 10% as atoms of Ni and/or Co;

II. 10% as atoms of one or more aliovalent or isovalent metals otherthan Ni or Co;

III. 10% as atoms of Fe(III); or

IV. any combinations of I. to III.;

-   -   M′ is a 3+ valency metal comprising at least one of Al³⁺, Y³⁺,        Nb³⁺, Ti³⁺, Ga³⁺, Cr³⁺ or V³⁺;    -   XO₄ is PO₄, alone or partially replaced by at most 10 mol % of        SO₄; and    -   0.03≦x≦0.15.    -   In yet another non-limiting embodiment, the present invention        relates to a carbon-deposited alkali metal phosphosilicate        cathode material, comprising particles which carry, on at least        a portion of their surface, carbon deposited by pyrolysis, where        the particles have the general formula        AM_(1-x)M′_(x)(XO₄)_(1-x)(SiO₄)_(x), where:

A is Li;

M is Fe(II);

M′ is a 3+ valency metal comprising at least one of Al³⁺, Y³⁺, Nb³⁺,Ti³⁺, Ga³⁺, Cr³⁺ or V³⁺;

XO₄ is PO₄; and

0.03≦x≦0.15.

In yet another non-limiting embodiment, the present invention relates toa carbon-deposited alkali metal phosphosilicate cathode material,comprising particles which carry, on at least a portion of theirsurface, carbon deposited by pyrolysis, where the particles have thegeneral formula AM_(1-x) M′_(x)(XO₄)_(1-x)(SiO₄)_(x), where:

A is Li;

M is Fe(II);

M′ is Y³⁺ or Al³⁺;

XO₄ is PO₄; and

0.03≦x≦0.15.

In yet another non-limiting embodiment, the present invention relates toa carbon-deposited alkali metal phosphosilicate cathode material,comprising particles which carry, on at least a portion of theirsurface, carbon deposited by pyrolysis, where the particles have thegeneral formula LiFe_(1-x)M″_(x)(PO₄)_(1-x)(SiO₄)_(x), where M″ is Y³⁺and/or Al³⁺, and 0.03≦x≦0.1, or 0.03≦x≦0.08, or 0.04≦x≦0.06.

In yet another non-limiting embodiment, the present invention relates toa carbon-deposited alkali metal phosphosilicate cathode material,comprising particles which carry, on at least a portion of theirsurface, carbon deposited by pyrolysis, where the particles have thegeneral formula LiFe_(0.9)M″_(0.1)(PO₄)_(0.9)(SiO₄)_(0.1,) where M″ isY³⁺ and/or Al³⁺.

In yet another non-limiting embodiment, the present invention relates toa carbon-deposited alkali metal phosphosilicate cathode material,comprising particles which carry, on at least a portion of theirsurface, carbon deposited by pyrolysis, where the particles have thegeneral formula LiFe_(0.95)M″_(0.05)(PO₄)_(0.95)(SiO₄)_(0.05,) where M″is Y³⁺ and/or Al³⁺.

Example 1 1-Step Solid-State Reaction

FePO₄.2H₂O (0.4 mole) serving as a phosphorus (P) and iron source, ironoxalate dihydrate (0.05 mole) serving as an iron source, Li₂CO₃ (0.25mole) serving as a lithium source, tetraethyl orthosilicate Si(OC₂H₅)₄(0.1 mole) serving as a silicon (Si) source, Zr(IV) acetate hydroxide(0.05 mole) serving as a Zr⁴⁺ source, at an atomic ratio ofLi:Fe:Zr:P:Si=1:0.9:0.1:0.8:0.2, and polymeric Unithox™ 550 (5 wt. % ofprecursors, manufactured by Baker Hughes) as a carbon source were mixedtogether in a mortar. The resulting mixture was heated at about 550° C.for about 6 hours under nitrogen atmosphere. The X-ray spectrum,represented in FIG. 1, of the resulting product showed formation ofLi₃PO₄, ZrO₂ and LiZr₂(PO₄)₃ impurity phases. The unit cell volume ofthe resulting olivine was 291 Å³.

Example 2 1-Step High-Energy Milling and 1-Step Solid-State Reaction

FePO₄.2H₂O (0.4 mole) serving as a phosphorus (P) and iron source, ironoxalate dihydrate (0.05 mole) serving as an iron source, Li₂CO₃ (0.25mole) serving as a lithium source, tetraethyl orthosilicate Si(OC₂H₅)₄(0.1 mole) serving as a silicon (Si) source, Zr(IV) acetate hydroxide(0.05 mole) serving as a Zr⁴⁺ source, at an atomic ratio ofLi:Fe:Zr:P:Si=1:0.9:0.1:0.8:0.2, and polymeric Unithox™ 550 (5 wt. % ofprecursors, manufactured by Baker Hughes) as a carbon source werehigh-energy milled in a SPEX Mill for about 2 hours. The resultinghigh-energy milled mixture was then heated at about 550° C. for about 6hours under nitrogen atmosphere. The X-ray spectrum, represented in FIG.2, of the resulting product showed formation of Li₃PO₄, ZrO₂ andLiZr₂(PO₄)₃ impurity phases. The unit cell volume of the resultingolivine was 291.1 Å³. The experiment has been repeated with similarresults by replacing the SPEX Mill with an Attritor® with abead/precursor ratio of 20:1.

Example 3 2-Step High-Energy Milling and 2-Step Solid-State Reaction,High Temperature

FePO₄.2H₂O (0.4 mole) serving as a phosphorus (P) and iron source, ironoxalate dihydrate (0.05 mole) serving as an iron source, Li₂CO₃ (0.25mole) serving as a lithium source, tetraethyl orthosilicate Si(OC₂H₅)₄(0.1 mole) serving as a silicon (Si) source, Zr(IV) acetate hydroxide(0.05 mole) serving as a Zr⁴⁺ source, at an atomic ratio ofLi:Fe:Zr:P:Si=1:0.9:0.1:0.8:0.2, and polymeric Unithox™ 550 (5 wt. % ofprecursors, manufactured by Baker Hughes) as a carbon source werehigh-energy milled in a SPEX Mill for 2 hours. The resulting high-energymilled mixture was then heated at about 550° C. for 6 hours undernitrogen atmosphere. The process was then repeated a second time usingthe same high-energy milling and heating conditions. In other words, asecond high-energy milling step and a second heating step were performedafter the above first heating step. The X-ray spectrum, represented inFIG. 3, of the resulting product showed formation of Li₃PO₄ and ZrO₂impurity phases. The unit cell volume of the resulting olivine is 291.8Å³. The experiment has been repeated with similar results by replacingthe SPEX Mill with an Attritor® with a bead/precursor ratio of 20:1.

Example 4 2-Step High-Energy Milling and 2-Step Solid-State Reaction,Low Temperature

FePO₄.2H₂O (0.4 mole) as a phosphorus (P) and iron source, iron oxalatedihydrate (0.05 mole) as an iron source, Li₂CO₃ (0.25 mole) as a lithiumsource, tetraethyl orthosilicate Si(OC₂H₅)₄ (0.1 mole) as a silicon (Si)source, Zr(IV) acetate hydroxide (0.05 mole) as a Zr⁴⁺ source, at anatomic ratio of Li:Fe:Zr:P:Si=1:0.9:0.1:0.8:0.2, and polymeric Unithox™550 (5 wt. % of precursors, manufactured by Baker Hughes) as a carbonsource were high-energy milled in a SPEX Mill for about 1 hour. Theresulting high-energy milled mixture was then heated at about 300° C.for about 1 hour under nitrogen atmosphere. Gaseous products evolvedduring this thermal step. The resulting product was then high-energymilled for about one hour with a SPEX Mill to produce an amorphousprecursor. The resulting high-energy milled amorphous precursor was thenheated at about 550° C. for about 5 hours under nitrogen atmosphere. TheX-ray spectrum of the resulting carbon-deposited lithium iron zirconiumphosphosilicate product, provided in FIG. 4, shows a unit cell volume of292.6 Å³ and no clear formation of impurity phase. The experiment hasbeen repeated with similar results by replacing the SPEX Mill with anAttritor® with a bead/precursor ratio of 20:1.

The experiment has been repeated with similar results by replacingZr(IV) acetate hydroxide with tetra n-butyl zirconate solution inbutanol (Tyzor® NBZ with approximately 87% active content in n-butanol,manufactured by Dorf Ketal) using a SPEX Mill and using the precursorsat same atomic ratio of Li:Fe:Zr:P:Si=1:0.9:0.1:0.8:0.2.

The experiment has also been repeated with similar results by replacingZr(IV) acetate hydroxide with bis[tri-n-butyltin(IV)]oxide (0.025 mole)as a Sn⁴⁺ source, using a SPEX Mill and using the precursors at anatomic ratio of Li:Fe:Sn:P:Si=1:0.9:0.1:0.8:0.2. This experimentproduced a carbon-deposited lithium iron tin phosphosilicate. Theexperiment has also been repeated with similar results by replacingZr(IV) acetate hydroxide with titanium(IV) 2-ethylhexyloxide (0.025mole) as a Ti⁴⁺ source, using a SPEX Mill and using the precursors at anatomic ratio of Li:Fe:Ti:P:Si=1:0.9:0.1:0.8:0.2. This experimentproduced a carbon-deposited lithium iron titanium phosphosilicate.

Results obtained from the above illustrative examples with Zr⁴⁺ aresummarized in the following Table 1.

TABLE 1 1^(st) 1^(st) 2^(nd) 2^(nd) cell volume % Name milling annealingmilling annealing (Å³) change Commercial 291 Reference C-LiFePO₄ 1-stepsolid-state none 550° C., 6 h none none 291   0% 1-step milling 2 hours550° C., 6 h none none 291.1  8.8% 2-step milling-high T 2 hours 550°C., 6 h 2 hours 550° C., 6 h 291.8 44.7% 2-step milling-low T 2 hours300° C., 6 h 2 hours 550° C., 6 h 292.6 91.2%

The results in Table 1 suggest that a reaction which includes a singlehigh-energy milling step of precursors prior to a thermal step providesan about 8.8% change in terms of unit cell volume relatively to the unitcell volume of commercial C—LiFePO₄. The results also suggest that areaction which includes two solid-state thermal steps and twohigh-energy milling steps prior to each of the thermal steps provides atleast an about 44.7% change in terms of unit cell volume relatively tothe unit cell volume of commercial C—LiFePO₄.

The results also suggest that a reaction which includes two solid-statethermal steps where the first thermal step is performed at a relativelylow temperature, i.e. about 300° C., in contrast to a relatively highertemperature, i.e. about 550° C., provides a higher % change in terms ofunit cell volume relatively to the unit cell volume of commercialC—LiFePO₄, e.g. 91.2% vs. 44.7%, respectively. Moreover, the inventorshave observed that a relatively high temperature during the secondthermal step could lead to a decomposition of the end-compound resultingimpurities phases, e.g. in the case of the illustrative end-compound ofthe examples the impurities phases include ZrO₂ and LiZr₂(PO₄)₃.

Example 5 2-Step High-Energy Milling and 2-Step Solid-State Reaction,Low Temperature

Iron oxalate dihydrate (590.11 g) serving as an iron source, Li₂CO₃(6.38 g) serving as a lithium source, LiH₂PO₄ (340.92 g) serving as aphosphorus (P) and lithium source, tetraethyl orthosilicate Si(OC₂H₅)₄(35.96 g) serving as a silicon (Si) source, Zr(IV) acetate hydroxide(36.63 g) serving as a Zr⁴⁺ source, at an atomic ratio ofLi:Fe:Zr:P:Si=1:0.95:0.05:0.95:0.05, stearic acid (13.7 g) and grade M5005 micronized polyethylene wax powders (13.7 g, manufactured by MarcusOil & Chemical), both as a carbon source, were charged in a high-energyball milling vertical agitation Attritor® (Union Process 1-S) containing10 kg of yttrium-stabilized ZrO₂ beads (10 mm diameter) as millingmedia. The Attritor® was then operated during 2 hours at a speed of 350rpm. The resulting high-energy milled mixture was then heated at about300° C. for about 1 hour under nitrogen atmosphere. Gaseous productsevolved during this thermal step. The resulting product was thenhigh-energy milled for about two hours in Attritor® to produce anamorphous precursor. The resulting high-energy milled amorphousprecursor was then heated at about 570° C. for about 6 hours under humidnitrogen gas (bubbled in water at around 80° C.), dry nitrogen gas isused during heating step (around 90 mn) and cooling step (around 180mn). The X-ray spectrum of the resulting carbon-deposited lithium ironzirconium phosphosilicate, provided in FIG. 5, shows a unit cell volumeof 291.3 Å³ and no clear formation of impurity phase.

The experiment has been repeated with similar results, with thefollowing precursors: iron oxalate dihydrate (576.19 g) serving as aniron source, Li₂CO₃ (12.46 g) serving as a lithium source, LiH₂PO₄(315.36 g) serving as a phosphorus (P) and lithium source, tetraethylorthosilicate Si(OC₂H₅)₄ (70.23 g) serving as a silicon (Si) source,Zr(IV) acetate hydroxide (35.76 g) serving as a Zr⁴⁺ source, at anatomic ratio of Li:Fe:Zr:P:Si=1:0.95:0.05:0.9:0.1, stearic acid (13.7 g)and grade M 5005 micronized polyethylene wax powders (13.7 g,manufactured by Marcus Oil & Chemical), both as a carbon source. TheX-ray spectrum of the resulting carbon-deposited lithium iron zirconiumphosphosilicate, provided in FIG. 6, shows a unit cell volume of 291.6Å³.

Example 6 2-Step High-Energy Milling and 2-Step Solid-State Reaction,Low Temperature

LiOH serving as lithium source, FePO₄ serving as an iron source andphosphorus (P) source, yttrium(III) 2-ethylhexanoate serving as a Y³⁺source, (NH₄)₂HPO₄ serving as a phosphorus (P) source, tetraethylorthosilicate Si(OC₂H₅)₄ serving as a silicon (Si) source, at an atomicratio Li:Fe:Y:P:Si=1:0.95:0.05:0.95:0.05, stearic acid (2.5 wt. % ofprecursors) and grade M 5005 micronized polyethylene wax powders (2.5wt. % of precursors), both as a carbon source were high-energy milled ina SPEX Mill and heat treated as described in example 4. Carbon-depositedlithium iron yttrium phosphosilicate was thus obtained.

The experiment has been repeated with similar results by replacingyttrium(III) 2-ethylhexanoate by aluminum 2,4-pentanedionate as a Al³⁺source, at an atomic ratio of Li:Fe:Al:P:Si=1:0.95:0.05:0.95:0.05.Carbon-deposited lithium iron aluminum phosphosilicate was thusobtained.

Example 7 2-Step High-Energy Milling and 2-Step Solid-State Reaction,Low Temperature

LiOH serving as lithium source, iron oxalate dihydrate serving as aniron source, MnO serving as a manganese source, Zr(IV) acetate hydroxideserving as a Zr⁴⁺ source, (NH₄)₂HPO₄ serving as a phosphorus (P) source,tetraethyl orthosilicate Si(OC₂H₅)₄ serving as a silicon (Si) source, atan atomic ratio Li:Fe:Mn:Zr:P:Si=1:0.8:0.15:0.05:0.9:0.1, stearic acid(2.5 wt. % of precursors) and grade M 5005 micronized polyethylene waxpowders (2.5 wt. % of precursors), both as a carbon source werehigh-energy milled in a SPEX Mill and heat treated as described inexample 4. Carbon-deposited lithium iron manganese zirconiumphosphosilicate was thus obtained.

The experiment has been repeated with similar results using the sameprecursors but at an atomic ratio ofLi:Fe:Mn:Zr:P:Si=1:0.5:0.45:0.05:0.9:0.1 and also at an atomic ratio ofLi:Fe:Mn:Zr:P:Si=1:0.2:0.75:0.05:0.9:0.1. In both cases,carbon-deposited lithium iron manganese zirconium phosphosilicate wasthus obtained.

Example 8 2-Step High-Energy Milling and 2-Step Solid-State Reaction,Low Temperature

Li₂CO₃ serving as lithium source, Na₂CO₃ serving as sodium source, ironoxalate dihydrate serving as an iron source, Zr(IV) acetate hydroxideserving as a Zr⁴⁺ source, LiH₂PO₄ serving as a phosphorus (P) source andlithium source, tetraethyl orthosilicate Si(OC₂H₅)₄ serving as a silicon(Si) source, at an atomic ratioLi:Na:Fe:Zr:P:Si=0.95:0.05:0.95:0.05:0.9:0.1, stearic acid (2.5 wt. % ofprecursors) and grade M 5005 micronized polyethylene wax powders (2.5wt. % of precursors), both as a carbon source were high-energy milled ina SPEX Mill and heat treated as described in example 4. Carbon-depositedlithium sodium iron zirconium phosphosilicate was thus obtained.

The experiment has been repeated with similar results using the sameprecursors but at an atomic ratio ofLi:Na:Fe:Zr:P:Si=0.85:0.15:0.95:0.05:0.9:0.1 and also at an atomic ratioof Li:Na:Fe:Zr:P:Si=0.75:0.25:0.95:0.05:0.9:0.1. In both cases,carbon-deposited lithium sodium iron zirconium phosphosilicate was thusobtained.

Example 9 2-Step High-Energy Milling and 2-Step Solid-State Reaction,Low Temperature

Li₂CO₃ serving as lithium source, iron oxalate dihydrate serving as aniron source, Zr(IV) acetate hydroxide serving as a Zr⁴⁺ source, LiH₂PO₄serving as a phosphorus (P) source and lithium source, tetraethylorthosilicate Si(OC₂H₅)₄ serving as a silicon (Si) source, at an atomicratio Li:Fe:Zr:P:Si=1.03:0.95:0.05:0.9:0.1, stearic acid (1.5 wt. % ofprecursors) and grade M 5005 micronized polyethylene wax powders (1.5wt. % of precursors), both as a carbon source were high-energy milled ina SPEX Mill and heat treated as described in example 4. Carbon-depositedlithium iron zirconium phosphosilicate was thus obtained.

The experiment has been repeated with similar results using the sameprecursors at an atomic ratio of Li:Fe:Zr:P:Si=0.97:0.95:0.05:0.9:0.1.Carbon-deposited lithium iron zirconium phosphosilicate was thusobtained.

Example 10 2-Step High-Energy Milling and 2-Step Solid-State Reaction,Low Temperature

Li₂CO₃ serving as lithium source, iron oxalate dihydrate serving as aniron source, niobium(V) ethoxide serving as a Nb⁵⁺ source, LiH₂PO₄serving as a phosphorus (P) source and lithium source, tetraethylorthosilicate Si(OC₂H₅)₄ serving as a silicon (Si) source, at an atomicratio Li:Fe:Nb:P:Si=1:0.97:0.03:0.91:0.09, stearic acid (2 wt. % ofprecursors) and grade M 5005 micronized polyethylene wax powders (2 wt.% of precursors), both as a carbon source were high-energy milled in aSPEX Mill and heat treated as described in example 4. Carbon-depositedlithium iron niobium phosphosilicate was thus obtained.

The experiment has been repeated with similar results by replacingniobium(V) ethoxide by tantalum(V) butoxide as a Ta⁵⁺ source, at anatomic ratio of Li:Fe:Ta:P:Si=1:0.98:0.02:0.94:0.06. Carbon-depositedlithium iron tantalum phosphosilicate was thus obtained.

Example 11 2-Step High-Energy Milling and 2-Step Solid-State Reaction,Low Temperature

Li₂CO₃ serving as lithium source, iron oxalate dihydrate serving as aniron source, cobalt(II) oxalate dihydrate serving as a cobalt source,Zr(IV) acetate hydroxide serving as a Zr⁴⁺ source, LiH₂PO₄ serving as aphosphorus (P) source and lithium source, tetraethyl orthosilicateSi(OC₂H₅)₄ serving as a silicon (Si) source, at an atomic ratioLi:Fe:Co:Zr:P:Si=1:0.9:0.05:0.05:0.9:0.1, stearic acid (2.5 wt. % ofprecursors) and grade M 5005 micronized polyethylene wax powders (2.5wt. % of precursors), both as a carbon source were high-energy milled ina SPEX Mill and heat treated as described in example 4. Carbon-depositedlithium iron cobalt zirconium phosphosilicate was thus obtained.

The experiment has been repeated with similar results by replacingcobalt(II) oxalate dihydrate by nickel oxalate dihydrate as a nickelsource, at an atomic ratio of Li:Fe:Ni:Zr:P:Si=1:0.9:0.05:0.05:0.9:0.1.Carbon-deposited lithium iron nickel zirconium phosphosilicate was thusobtained.

Example 12 2-Step High-Energy Milling and 2-Step Solid-State Reaction,Low Temperature

Li₂CO₃ serving as lithium source, iron oxalate dihydrate serving as aniron source, MnO serving as a manganese source, magnesiumacetylacetonate dihydrate as magnesium source, Zr(IV) acetate hydroxideserving as a Zr⁴⁺ source, LiH₂PO₄ serving as a phosphorus (P) source andlithium source, tetraethyl orthosilicate Si(OC₂H₅)₄ serving as a silicon(Si) source, at an atomic ratioLi:Fe:Mn:Mg:Zr:P:Si=1:0.8:0.1:0.05:0.05:0.9:0.1, stearic acid (2.5 wt. %of precursors) and grade M 5005 micronized polyethylene wax powders (2.5wt. % of precursors), both as a carbon source were high-energy milled ina SPEX Mill and heat treated as described in example 4. Carbon-depositedlithium iron manganese magnesium zirconium phosphosilicate was thusobtained.

The experiment has been repeated with similar results using the sameprecursors but at an atomic ratio ofLi:Fe:Mn:Mg:Zr:P:Si=1:0.45:0.45:0.05:0.05:0.9:0.1 and also at an atomicratio of Li:Fe:Mn:Mg:Zr:P:Si=1:0.2:0.7:0.05:0.05:0.9:0.1. In both cases,carbon-deposited lithium iron manganese magnesium zirconiumphosphosilicate was thus obtained.

Example 13 2-Step High-Energy Milling and 2-Step Solid-State Reaction,Low Temperature

Iron oxalate dihydrate (590.11 g) serving as an iron source, Li₂CO₃(6.38 g) serving as a lithium source, LiH₂PO₄ (340.92 g) serving as aphosphorus (P) and lithium source, tetraethyl orthosilicate Si(OC₂H₅)₄(35.96 g) serving as a silicon (Si) source, Zr(IV) acetate hydroxide(36.63 g) serving as a Zr⁴⁺ source, at an atomic ratio ofLi:Fe:Zr:P:Si=1:0.95:0.05:0.95:0.05, stearic acid (9.13 g) and grade M5005 micronized polyethylene wax powders (9.13 g, manufactured by MarcusOil & Chemical), both as a carbon source, were charged in a high-energyball milling vertical agitation Attritor® (Union Process 1-S) containing10 kg of yttrium-stabilized ZrO₂ beads (10 mm diameter) as millingmedia. The Attritor® was then operated during 2 hours at a speed of 350rpm. The resulting high-energy milled mixture was then heated at about300° C. for about 1 hour under nitrogen atmosphere. Gaseous productsevolved during this thermal step. The resulting product, stearic acid(4.57 g) and grade M 5005 micronized polyethylene wax powders (4.57 g),both as a carbon source, were then high-energy milled for about one hourin Attritor®. The resulting high-energy milled amorphous precursor wasthen heated at about 570° C. for about 6 hours under humid nitrogen gas(bubbled in water at around 80° C.), dry nitrogen gas is used duringheating step (around 90 mn) and cooling step (around 180 mn).Carbon-deposited lithium iron zirconium phosphosilicate was thusobtained.

Example 14 Electrochemical Characterization

Liquid electrolyte batteries were prepared according to the followingprocedure.

A cathode material of the present invention, PVdF-HFP copolymer(supplied by Atochem), and EBN-1010 graphite powder (supplied bySuperior Graphite) were ball milled in a jar mill with zirconia beads inN-methylpyrrolidone (NMP) for 10 hours in order to obtain a dispersioncomposed of the cathode/PVdF-HFP/graphite 80/10/10 by weight mixture.The mixture obtained was subsequently deposited, using a Gardner®device, on a sheet of aluminum carrying a carbon-treated coating(supplied by Exopack Advanced Coating) and the film deposited was driedunder vacuum at 80° C. for 24 hours and then stored in a glovebox. Abattery of the “button” type was assembled and sealed in a glovebox, usebeing made of the carbon-treated sheet of aluminum carrying the coatingcomprising the carbon-deposited alkali metal phosphosilicate, ascathode, a film of lithium, as anode, and a separator having a thicknessof 25 μm (supplied by Celgard) impregnated with a 1M solution of LiPF₆in an EC/DEC 3/7 mixture.

The batteries were subjected to scanning cyclic voltammetry at ambienttemperature with a rate of 20 mV/80 s using a VMP2 multichannelpotentiostat (Biologic Science Instruments), first in oxydation from therest potential up to 4 V and then in reduction between 4 and 2.2 V.Voltammetry was repeated a second time and capacity of the cathodematerial (C in mAh/g) determined from the second reduction cycle.

Some batteries were subjected to C/12 galvanostatic cycling at 60° C.between 2.2 and 4 Volt.

Some batteries were subjected to power capability test at ambienttemperature (ragone plot), by determining capacity (in mAh/g) atdifferent discharge rate (C-rate; a 1 C rate corresponding to dischargeof full capacity in 1 hour).

The following clauses provide a further description of examples of aprocess in accordance with the present invention:

CLAUSES

1. A process for the synthesis of a carbon-deposited alkali metaloxyanion cathode material comprising particles, wherein said particlescarry, on at least a portion of the particle surface, carbon depositedby pyrolysis, said process comprising:

a first dry high-energy milling step performed on precursors of saidcarbon-deposited alkali metal oxyanion prior to a first solid-statethermal reaction, wherein said first solid-state thermal reactionproduces a first solid-state thermal reaction product; and

a second dry high-energy milling step performed on said product prior toa second solid-state thermal reaction.

2. The process of clause 1, wherein said process comprises adding asource compound of carbon to said precursors prior to or during saidfirst high-energy milling step and/or to said product prior to or duringsaid second high-energy milling step.

3. The process of clause 2, wherein said carbon source is a liquid,solid or gaseous hydrocarbon.

4. The process of clause 3, wherein said carbon source is selected fromthe group consisting of polycyclic aromatic entities, perylene and itsderivatives, polyhydric compounds, cellulose, starch and their estersand ethers, polyolefins, polybutadienes, polyvinyl alcohol, condensationproducts of phenols, and polymers derived from furfuryl alcohol, fromstyrene, from divinylbenzene, from naphthalene, from perylene, fromacrylonitrile and from vinyl acetate.

5. The process of clause 4, wherein said polycyclic aromatic entitiesare selected from the group consisting of tar and pitch.

6. The process of clause 4, wherein said polyhydric compounds areselected from the group consisting of sugars, carbohydrates, and theirderivatives.

7. The process of any one of clauses 1 to 6, wherein said precursorscomprise at least one source compound of an alkali metal, at least onesource compound of Fe and/or Mn; at least one source compound of a metalM′, where M′ is a 2+ or more metal in the carbon-deposited alkali metaloxyanion; and at least one source compound of an oxyanion, if theoxyanion is not present in another source compound.

8. The process of clause 7, wherein said source of oxyanion comprises asource compound of phosphorus (P), if the element P is not present inanother source compound; and at least one source compound of silicon(Si)

9. The process of clause 7 or clause 8, wherein said source compound ofM is selected from the group consisting of iron(III) oxide, magnetite(Fe₃O₄), trivalent iron phosphate, lithium iron hydroxyphosphate,trivalent iron nitrate, ferrous phosphate, vivianite Fe₃(PO₄)₂, ironacetate (CH₃COO)₂Fe, iron sulfate (FeSO₄), iron oxalate, ammonium ironphosphate (NH₄FePO₄), and any combinations thereof.

10. The process of any one of clauses 7 to 9, wherein said sourcecompound of M is selected from the group consisting of MnO, MnO₂,manganese acetate, manganese oxalate, manganese sulfate, manganesenitrate, and any combinations thereof.

11. The process of any one of clauses 7 to 10, wherein said sourcecompound of alkaline metal is selected from the group consisting oflithium oxide, lithium hydroxide, lithium carbonate, Li₃PO₄, LiH₂PO₄,lithium ortho-, meta- or polysilicates, lithium sulfate, lithiumoxalate, lithium acetate, and any combinations thereof.

12. The process of any one of clauses 7 to 11, wherein said sourcecompound of P is selected from the group consisting of phosphoric acidand its esters, Li₃PO₄, LiH₂PO₄, monoammonium or diammonium phosphates,trivalent iron phosphate, manganese ammonium phosphate, and anycombinations thereof.

13. The process of any one of clauses 7 to 12, wherein said sourcecompound of Si is selected from the group consisting of tetraorthosilicate, nanosized SiO₂, Li₂SiO₃, Li₄SiO₄, and any combinationsthereof.

14. The process of any one of clauses 7 to 12, wherein said sourcecompound of a 2+ or more valency metal is a source compound of a 4+valency metal selected from the group consisting of Zr⁴⁺, Ti⁴⁺, Nb⁴⁺,Mo⁴⁺, Ge⁴⁺, Ce⁴⁺ and Sn^(4±).

15. The process of clause 14, wherein said 4+ valency metal is Zr⁴⁺ andsaid source compound is selected from the group consisting of zirconiumacetate hydroxide, zirconium alkoxide, and a combination thereof.

16. The process of any one of clauses 7 to 15, wherein said sourcecompounds are selected to provide after said second thermal treatment acathode material having alkali metal:M:M′:P:Si ratios of about 1:1:0.7to 1:>0 to 0.3.

17. The process of any one of clauses 1 to 16, wherein said high-energymilling steps are performed with a milling apparatus selected from thegroup consisting of a high-energy ball mill, a pulverizing mixer mill, aplanetary ball mill, a drum/ball-mill, a shaker mill, a stirred ballmill, a mixer ball mill, a vertical attritor, and a horizontal attritor.

18. The process of any one of clauses 1 to 17, wherein said firstsolid-state thermal step is operated at a temperature selected from therange of temperatures between about 200° C. and about 600° C.

19. The process of any one of clauses 1 to 18, wherein said secondsolid-state thermal step is operated at a temperature selected from therange of temperatures between about 400° C. and about 800° C.

20. The process of any one of clauses 1 to 18, wherein said first and/orsecond solid-state thermal step(s) is performed under an inert orreductive atmosphere.

21. The process of any one of clauses 1 to 20, wherein said first and/orsecond high-energy milling step(s) is performed under an inert orreductive atmosphere.

22. The process of clause 20 or 21, wherein said reductive atmosphereparticipates in the reduction or prevents the oxidation of the oxidationstate of at least one metal in the precursors without full reduction toan elemental state.

23. The process of any one of clauses 20 to 22, wherein said reductiveatmosphere comprises an externally applied reductive atmosphere, areductive atmosphere derived from the degradation of a compound, areductive atmosphere derived from the synthesis reaction, or anycombinations thereof.

24. The process of clause 23, wherein said externally applied reductiveatmosphere comprises CO, H₂, NH₃, HC, and any combinations thereof,wherein HC is a hydrocarbon or carbonaceous product.

25. The process of clause 23 or 24, wherein said reductive atmospherederived from the degradation of a compound comprises a reductiveatmosphere which is produced when the compound is degraded or istransformed under heat.

26. The process of clause 23, wherein said reductive atmosphere derivedfrom the degradation of a compound comprises CO, CO/CO₂, H₂ or anycombinations thereof.

27. The process of any one of clauses 1 to 24, wherein said precursorscomprise FePO₄, iron oxalate, Li₂CO₃, tetraethyl orthosilicate andZr(IV) acetate hydroxide.

28. A process for the synthesis of a carbon-deposited phosphosilicatecathode material comprising particles of a compound corresponding to thegeneral formula AM_(1-x) M′_(x)(XO₄)_(1-x)(SiO₄)_(2x) which carry, on atleast a portion of the particle surface, carbon deposited by pyrolysis,wherein

A is Li, alone or partially replaced by at most 30% as atoms of Naand/or K;

M is a metal comprising at least 90% at. of Fe(II), or Mn(II), or amixture thereof;

M′ is at least one 2+ or more valency metal;

XO₄ is PO₄, alone or partially replaced by at most 30 mol % of SO₄; and

0.05≦x≦0.15

said process comprising reacting precursors of said compound in at leastone solid-state thermal step and wherein at least one high-energymilling step is performed on said reacting precursors prior to said atleast one thermal step.

29. The process according to clause 28, wherein said precursors comprise

a) at least one source compound of A;

b) at least one source compound of M;

c) at least one source compound of M′;

d) at least one source compound of P, if the P is not in another sourcecompound; and

e) at least one source compound of Si, if the Si is not in anothersource compound.

30. A process for the synthesis of an alkali metal oxyanion cathodematerial comprising particles, wherein said particles carry, on at leasta portion of the particle surface, carbon deposited by pyrolysis, saidprocess comprising a first high-energy milling step performed onprecursors of said alkali metal oxyanion prior to a first solid-statethermal reaction.

31. A process as defined in clause 30, wherein said first solid-statethermal reaction produces a first solid-state thermal reaction product;and wherein a second high-energy milling step is performed on saidproduct prior to a second solid-state thermal reaction.

32. A process as defined in any of clauses 30 and 31, wherein saidprecursors comprise:

a) at least one source compound of an alkaline metal;

b) at least one source compound of Fe and/or Mn;

c) at least one source compound of a metal having a valence of 2+ ormore;

d) at least one source compound of an oxyanion, if the oxyanion is notin another source compound; and

e) a source of carbon.

33. A process as defined in clause 31, wherein said precursors comprise:

a) at least one source compound of an alkaline metal;

b) at least one source compound of Fe and/or Mn;

c) at least one source compound of a metal having a valence of 2+ ormore;

d) at least one source compound of an oxyanion, if the oxyanion is notin another source compound; and

e) a source of carbon,

wherein said source compounds are totally present in said first thermalstep, or any part thereof is present in each of the first and secondthermal step.

The person skilled in the art will understand that while the workingexamples illustrate an embodiment where the oxyanion is aphosphosilicate, other variations, modifications and refinements arepossible within the spirit and scope of the present invention. Forexample, U.S. Pat. No. 6,085,015, which is herein incorporated byreference in its entirety, discloses that the orthosilicate anion beingisosteric with the sulfate, phosphate, germanate and vanadate anions,the corresponding elements can easily replace silicon in this types ofstructure, as does boron and aluminum, offering a wide choice ofmaterials with complete control of the charge density on the anionicsites. Another example, U.S. Pat. No. 6,514,640 which is hereinincorporated by reference in its entirety, discloses “isochargesubstitutions” that refers to substitution of one element on a givencrystallographic site with an element having a similar charge. Forexample, Mg²⁺ is considered similarly isocharge with Fe²⁺ and V⁵⁺ issimilarly isocharge with P⁵⁺. Likewise, (PO₄)₃ tetrahedra can besubstituted with (VO₄)₃ tetrahedra. “Aliovalent substitution” refers tosubstitution of one element on a given crystallographic site with anelement of a different valence or charge. One example of an aliovalentsubstitution would be Cr³⁺ or Ti⁴⁺ on an Fe²⁺ site.

The above description of the embodiments should not be interpreted in alimiting manner since other variations, modifications and refinementsare possible within the spirit and scope of the present invention. Thescope of the invention is defined in the appended claims and theirequivalents.

All of the compositions and/or process disclosed and claimed herein canbe made and executed without undue experimentation in light of thepresent disclosure. While the compositions and process of this inventionhave been described in terms of preferred embodiments, it will beapparent to those of skill in the art that variations can be applied tothe compositions and/or process and in the steps or in the sequence ofsteps of the process described herein without departing from theconcept, spirit and scope of the invention. All such similar substitutesand modifications apparent to those skilled in the art are deemed to bewithin the spirit, scope and concept of the invention as defined by theappended claims.

All of the references cited in this document are hereby eachincorporated herein by reference in their entirety.

The invention claimed is:
 1. A process for the synthesis ofphosphosilicate cathode material particles having a deposit of carbon onat least a portion of the surface thereof, said phosphosilicate materialcomprising lithium and Fe, said Fe being doped with a 4+ valence statemetal M′, said process comprising: a first dry high-energy milling stepperformed on precursors of said cathode material; a first solid-statethermal reaction; a second dry high-energy milling step; and a secondsolid-state thermal reaction.
 2. The process of claim 1, wherein saidfirst solid-state thermal reaction is operated at a temperature selectedfrom the range of temperatures of from about 200° C. to about 600° C. 3.The process of claim 1, wherein said second solid-state thermal reactionis operated at a temperature selected from the range of temperatures offrom about 400° C. to about 800° C.
 4. The process of claim 1, whereinsaid first and/or second high-energy milling step is performed during atime period selected from the range of from about 5 minutes to about 4hours.
 5. The process of claim 1, further comprising a subsequent flashthermal treatment which is operated at a temperature selected from thetemperature range of from about 650° C. to about 900° C.
 6. The processof claim 1, wherein said precursors include a source compound of carbonfor obtaining the deposit of carbon.
 7. The process of claim 6, whereinsaid source compound of carbon is a liquid, solid or gaseoushydrocarbon.
 8. The process of claim 1, wherein said Fe is doped withfrom 3 atomic % to 15 atomic % of the 4+ valence state M′.
 9. Theprocess of claim 1, wherein said precursors comprise at least one sourcecompound of lithium, at least one source compound of Fe; at least onesource compound of said 4+ valence state metal M′; at least one sourcecompound of phosphorus; at least one source compound of silicon; and atleast one source of carbon.
 10. The process of claim 9, wherein said atleast one source compound of Fe is selected from the group consisting ofiron, iron(III) oxide, magnetite (Fe₃O₄), trivalent iron phosphate,lithium iron hydroxyphosphate, trivalent iron nitrate, ferrousphosphate, vivianite Fe₃(PO₄)₂, iron acetate (CH₃COO)₂Fe, iron sulfate(FeSO₄), iron oxalate, iron(III) nitrate, iron(II) nitrate, FeCl₃,FeCl₂, FeO, ammonium iron phosphate (NH₄FePO₄), Fe₂P₂O₇, ferrocene, andany combinations thereof.
 11. The process of claim 9, wherein said atleast one source compound of lithium is selected from the groupconsisting of lithium oxide, lithium hydroxide, lithium carbonate,Li₃PO₄, LiH₂PO₄, LiNaHPO₄, LiKHPO₄, Li₂HPO₄, lithium ortho-, meta- orpolysilicates, lithium sulfate, lithium oxalate, lithium acetate, andany combinations thereof.
 12. The process of claim 9, wherein said atleast one source compound of silicon is selected from the groupconsisting of organosilicon, silicon alkoxides, tetraalkylorthosilicate, tetraethyl orthosilicate, nanosized SiO₂, Li₂SiO₃,Li₄SiO₄, and any combinations thereof.
 13. The process of claim 1,wherein said M′ is selected from the group consisting of Zr⁴⁺, Ti⁴⁺,Nb⁴⁺, Mo⁴⁺, Ge⁴⁺, Ce⁴⁺ and Sn⁴⁺.
 14. The process of claim 1, whereinsaid M′ is Zr⁴⁺.
 15. The process of claim 14, wherein said at least onesource compound of M′ is selected from the group consisting of zirconiumacetate hydroxide, zirconium alkoxide, n-butyl zirconate, zirconium(IV)acetylacetonate, zirconium(IV) ethoxide, zirconium(IV)hydrogenphosphate, zirconium(IV) silicate and any combinations thereof.16. The process of claim 14, wherein said source compounds are selectedto provide a cathode material having a general element ratiosLi:(Fe+Zr):PO₄:SiO₄ of about 1:1:0.7 to less than 1: more than 0 to 0.3.17. The process of claim 1, wherein said second dry high-energy millingstep produces a substantially amorphous material.
 18. The process ofclaim 1, wherein said first and/or second solid-state thermal reactionsis performed under an inert or reductive atmosphere.
 19. The process ofclaim 1, wherein said precursors comprise at least FePO₄ and Li₂CO₃. 20.The process of claim 1, said material further comprising Mn.